chore(frontends/lean): remove dead code
chore(frontends/lean): remove dead code

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

fgdorais/lean,sp3ctum/lean,fgdorais/lean,sp3ctum/lean,soonhokong/lean-windows,digama0/lean,soonhokong/lean-osx,levnach/lean,fpvandoorn/lean,Kha/lean,eigengrau/lean,digama0/lean,htzh/lean,leodemoura/lean,avigad/lean,leodemoura/lean,dselsam/lean,leodemoura/lean,digama0/lean,leodemoura/lean,eigengrau/lean,javra/lean,johoelzl/lean,soonhokong/lean-windows,digama0/lean,johoelzl/lean,dselsam/lean,leanprover-community/lean,javra/lean,soonhokong/lean-windows,c-cube/lean,UlrikBuchholtz/lean,rlewis1988/lean,UlrikBuchholtz/lean,UlrikBuchholtz/lean,levnach/lean,htzh/lean,htzh/lean,fpvandoorn/lean2,johoelzl/lean,javra/lean,leodemoura/lean,fpvandoorn/lean,levnach/lean,avigad/lean,eigengrau/lean,fgdorais/lean,soonhokong/lean,soonhokong/lean-osx,dselsam/lean,leanprover/lean,leanprover/lean,fgdorais/lean,soonhokong/lean,rlewis1988/lean,fpvandoorn/lean,leodemoura/lean,avigad/lean,Kha/lean,johoelzl/lean,sp3ctum/lean,leanprover/lean,dselsam/lean,avigad/lean,soonhokong/lean-windows,levnach/lean,javra/lean,leanprover-community/lean,leanprover/lean,rlewis1988/lean,Kha/lean,UlrikBuchholtz/lean,c-cube/lean,Kha/lean,soonhokong/lean-osx,soonhokong/lean,soonhokong/lean,leanprover-community/lean,UlrikBuchholtz/lean,c-cube/lean,soonhokong/lean-osx,rlewis1988/lean,avigad/lean,eigengrau/lean,leanprover/lean,leanprover-community/lean,sp3ctum/lean,fpvandoorn/lean2,fpvandoorn/lean2,fpvandoorn/lean2,fpvandoorn/lean,soonhokong/lean,fpvandoorn/lean,fgdorais/lean,Kha/lean,fpvandoorn/lean,leanprover/lean,levnach/lean,johoelzl/lean,soonhokong/lean-osx,Kha/lean,johoelzl/lean,fgdorais/lean,sp3ctum/lean,eigengrau/lean,c-cube/lean,digama0/lean,digama0/lean,htzh/lean,dselsam/lean,leanprover-community/lean,fpvandoorn/lean2,dselsam/lean,avigad/lean,rlewis1988/lean,soonhokong/lean-windows,c-cube/lean,leanprover-community/lean,rlewis1988/lean,htzh/lean,javra/lean